Cricket and tunnels.

I would generally agree with this statement.

The classification of structures on LU appears quite arbitrary. Covered ways on LU are structurally speaking no different to a bridge*. The LU definition for a covered way is "a structure spanning over the system whose length is twice its span" though I don’t where this might originate. I believe NR’s definition for a covered way differs.

The brick arch structures spanning over the sub-surface railway are referred to as tunnels by LU though the majority of these were constructed using the same cut and cover methods as covered ways with temporary centring timbers to form the arch rings. The logic in the classification is that the structural behaviour of arches is quite different to covered way structures and has more in common with the deep level tube tunnels. It is not uncommon for covered ways to however have jack arches as decking. A bored tunnel was constructed under Clerkenwell though internally it appears no different to the other brick tunnels on the SSR. Incidentally, Gerard’s Cross Tunnel is structurally an arch and the failure to understand its behaviour led to the partial collapse of the first attempt.

Confusingly, LU retaining wall assets have the same W- prefix as parapet walls. Gabion basket type retaining structures use the RW- prefix.

* Just something I wanted to clarify Railway engineers would describe a bridge supporting the line as an underline- or underbridge and a bridge over the line as an overbridge. Simple. However, the definitions are reversed for Highway engineers.